It is known that presently the WITTIG-HORNER reaction is used to produce alkenes from aldehydes and to introduce acid, ester, nitrile, etc . . . functions on the ethylenic double bond. The object of this reaction is the preparation of an ethylene ester and comprises placing the initial aldehyde in the presence of the following reagents: phosphonate and base, in an inert organic solvent (J. SEYDEN-PENNE et al, Tetrahedron, 1972, p 4209; Tetrahedron, 1973, p 2437, and Journal of Organic Chemistry, 1980, p 1270; C. PIECHUCKI, Synthesis, 1974, 869; M. MIKOLAJCZYK et al, Synthesis, 1976, p396; J. KOVAC et al, Collection Czechoslovakia Chemical Communications, 1976, p 764; E. BREUER et al, Tetrahedron, 1978, p 924; A. FOUCAUD et al, Tetrahedron Letters, 1980, p 2161 and Synthesis, 1979, p 884; J. VILLERAS et al, Synthesis, 1983, p 300 and Phosphorus and Sulfur, 1983, p 385). An improved method is described in the French patent application # 81.17825 and U.S. Pat. No. 4,501,910 in the name of applicant; this method employs an alcohol as the solvent.
In all these methods, the base allows taking a porton off the phosphorus' alpha-carbon. The reactive entity so formed condenses with the aldehyde carbonyl function to result in an intermediary oxy-anion which thereafter changes toward the ethylene ester. Rigorously speaking the organic solvent does not constitute a reagent of this reaction and is not used up in it even if the method of the application No. 81.17825 and U.S. Pat. No. 4,501,910 is improved by this solvent as to the yield of the desired type of alkene.
The above cited reactions necessarily result in an ethylenic ester of which the radicals are obtained from the phosphonate. However, presently few phosphonates are commercially available and as a matter of fact, with respect to low-cost products, solely the methyl or ethyl phosphonates are commercially offered. Accordingly only the ethylene esters of methyl or ethyl given by the formula below ##STR1## have been synthesized by the WITTIG-HORNER and derivative reactions.
Of course it is always possible to substitute thereafter the ethyl or methyl radical by a new and desired radical by means of a transesterification reaction. However this double reaction requires a first extraction of the ethyl or methyl ethylene ester at the end of the WITTIG-HORNER reaction and then a second extraction with the object of isolating the desired ethylene ester. Besides the constraints resulting from implementing two consecutive reactions, this procedure also results in a notable drop in yields because the overall yield is the product of the particular yields of the two reactions and the two extractions.
An object of the present invention is to eliminate the above-stated limmitations placed on the WITTIG-HORNER reaction by creating a process allowing to convert directly, and in a single operation which is free of any intermediate separation, an aldehyde into an ethylene ester of the formula ##STR2## where R.sub.2 is a hydrocarbon radical other than methyl or ethyl and selected by the operator.
Another object of the invention is to create a conversion procedure which allows a very high yield of ethylenic ester.